Solutions of ferrous and ferric iron salts have well established utility in numerous scenarios in the treatment of potable water and wastewaters. Ferrous solutions can also be used as base material in the manufacture of ferric chloride solution products which have separate market values in potable water and wastewater treatment applications.
One of the major sources of these iron salt solutions, of both sulfate and chloride anion, is from the titanium dioxide (TiO2) manufacturing processes, wherein the use of various grades of ilmanite or rutile type ores produces iron salt side streams with varying amounts of metal salt co-constituents. These metal salt co-constituents can include salts of a variety of metals, including titanium, chromium, zirconium, niobium, manganese and other metals in relatively high concentrations. In the TiO2 industry, these iron solutions are generally disposed by neutralization, dewatering, and landfill, or deepwelled as hazardous waste. In some cases, the solutions are purified and sold as ferrous chloride or ferric chloride solution for wastewater and potable water treatment. However, the chlorides and hydroxychlorides of titanium, niobium, and zirconium in these solutions slowly precipitate as fine solids. As these fine precipitates accumulate they will cause problems in storage and handling of the solutions at the customers' sites as the fine precipitates settle and subsequently clog tanks, strainers, and pumping lines. This equipment then needs to be taken out of service for cleaning, incurring costs and interruption of service.
All methodologies, to date, have been relatively ineffectual or are very inefficient in preventing or removing these precipitates from the materials and the industry has learned to adjust to the issue but with significant cost. Accordingly, the marketable value of the iron solution to the water treating industry will generally be inversely proportionate to the levels of co-constituents carried in the solution. Therefore, there is value in discovering methods of reducing the levels of co-constituents in the iron solutions. Furthermore, these iron solutions are produced in concentrations that are too low to provide viable market access. It is therefore advantageous to determine beneficial methods of concentrating iron.
There exists a need for an improved process for separating impurities, including metal salt co-constituents such as niobium, titanium, zirconium and other metal salt co-constituents, from these iron chloride solutions, leaving a stable iron chloride solution that does not precipitate fine solids.